On Saturday, 7 April 2018 11:25:57 UTC+1, Jeff Layman wrote:
On 07/04/18 09:31, The Natural Philosopher wrote:
On 07/04/18 09:18, Tim Lamb wrote:


In my experience the blockage will be the rainwater diverter itself.
Cleaning and re-fitting should clear the problem.

I'll second that. Rainwater diverters are crap.

Not IMHO. I've been using them for upwards of 10 years without problem.
I've never had one block and need cleaning out. BUT I do use gutter
guards
(https://www.screwfix.com/p/floplast-gutter-guards-100mm-black-10-pack/12515).
These do keep a lot of rubbish out, particularly leaves and moss.

When I inspect the gutters what I find is not just small amounts of
vegetable matter, but what could be sand or other mineral material. Is
it possible that concrete tiles weather and the surface slowly wears
away? These tiles are just over 50 years old.

Definitely. And they wear faster on shallow slopes due to more freeze-thaw damage.


NT